“…[1][2][3] Normally, cellular immunity keeps the virus quiescent where it is harbored (in the urinary tract, bone marrow, lymphoid tissue, and possibly the central nervous system). 2,4,5 However, patients with abnormalities in cell-mediated immunity are vulnerable to viral reactivation, and replication occurs in glial cells (predominantly oligodendrocytes) and neurons of the cerebrum and granular cell layer of the cerebellum. This leads to demyelination and neuronal death, causing mortality within 2 to 15 months of diagnosis; however, death usually occurs within 2 months for 90% of patients who also have a hematologic malignancy.…”